Intervertebral disc implants and tooling

ABSTRACT

A kit for preparing an intervertebral disc space for receiving an implant ( 100 ) includes a plurality of trials ( 152 ) having different sizes. Each trial ( 152 ) includes a body ( 154 ) insertible into an intervertebral disc space, the body ( 154 ) having a leading end ( 162 ), a trailing end ( 164 ), a top surface ( 156 ) and a bottom surface ( 160 ), the top surface of the body having a first groove ( 176 ) formed therein. Each implant also includes a flange ( 166 ) secured to the trailing end ( 164 ) of the body ( 154 ), the flange ( 166 ) having a first channel ( 180 ) aligned with the first groove ( 176 ), wherein each of the different sized trials has a different flange thickness. The flange thickness controls advancement of a cutting tool such as a chisel ( 192 ) into the first groove at the top surface of the trial body, which controls the depth of the cut into vertebral bone.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of U.S.Provisional Patent Application No. 60/846,196 filed Sep. 21, 2006, thedisclosure of which is hereby incorporated herein by reference.

The present application is related to U.S. patent application Ser. No.11/439,808, filed May 24, 2006, which claims the benefit of U.S.Provisional Patent Application No. 60/790,415, filed Apr. 7, 2006, whichclaims the benefit of U.S. Provisional Patent Application No.60/721,053, filed Sep. 27, 2005, which claims the benefit of U.S.Provisional Patent Application No. 60/701,306, filed Jul. 21, 2005,which claims the benefit of U.S. Provisional Patent Application No.60/685,295, filed May 27, 2005, the disclosures of which are herebyincorporated by reference herein.

The present application also relates to U.S. Pat. No. 6,908,484,entitled “Cervical Disc. Replacement” and filed on Mar. 6, 2003; U.S.Pat. No. 6,994,728, entitled “Cervical Disc Replacement Method” andfiled on Feb. 11, 2004; United States Patent Application Publication No.2004/0176851, entitled “Cervical Disc Replacement” and filed on Feb. 11,2004; U.S. Pat. No. 6,994,729, entitled “Cervical Disc Replacement” andfiled on Feb. 11, 2004; U.S. Pat. No. 6,997,955, entitled “Cervical DiscReplacement” and filed on Feb. 11, 2004; U.S. Pat. No. 6,972,037,entitled “Cervical Disc Replacement” and filed on Feb. 11, 2004; U.S.Pat. No. 6,972,038, entitled “Cervical Disc Replacement” and filed onFeb. 11, 2004; U.S. Pat. No. 6,997,954, entitled “Cervical DiscReplacement Method” and filed on Feb. 11, 2004; United States PatentApplication Publication No. 2005/0240272, entitled “Cervical DiscReplacement” and filed on May 9, 2005; United States Patent ApplicationPublication No. 2005/0240271, entitled “Cervical Disc Replacement” andfiled on May 9, 2005; United States Patent Application Publication No.2005/0240270, entitled “Cervical Disc Replacement” and filed on May 9,2005; U.S. Pat. No. 6,896,676, entitled “Instrumentation And Methods ForUse In Implanting A Cervical Disc Replacement Device” and filed on Oct.17, 2003; United States Patent Application Publication No. 2004/0176773,entitled “Instrumentation And Methods For Use In Implanting A CervicalDisc Replacement Device” and filed on Feb. 18, 2004; United StatesPatent Application Publication No. 2004/0176843, entitled“Instrumentation And Methods. For Use In Implanting A Cervical DiscReplacement Device” and filed on Feb. 18, 2004; United States PatentApplication Publication No. 2004/0176778, entitled “Instrumentation AndMethods For Use In Implanting A Cervical Disc Replacement Device” andfiled on Feb. 18, 2004; United States Patent Application Publication No.2004/0176777, entitled “Instrumentation And Methods For Use InImplanting A Cervical Disc Replacement Device” and filed on Feb. 18,2004; United States Patent Application Publication No. 2004/0176852,entitled “Instrumentation And Methods For Use In Implanting A CervicalDisc Replacement Device” and filed on Feb. 18, 2004; United StatesPatent Application Publication No. 2004/0176774, entitled“Instrumentation And Methods For Use In Implanting A Cervical DiscReplacement Device” and filed on Feb. 18, 2004; United States PatentApplication Publication No. 2004/0176772, entitled “Instrumentation AndMethods For Use In Implanting A Cervical Disc Replacement Device” andfiled on Feb. 18, 2004; United States Patent Application Publication No.2004/0220590, entitled “Instrumentation And Methods For Use InImplanting A Cervical Disc Replacement Device” and filed on Feb. 18,2004; United States Patent Application Publication No. 2005/0071013,entitled “Instrumentation And Methods For Use In Implanting A CervicalDisc Replacement Device” and filed on Nov. 19, 2004; and United StatesPatent Application Publication No. 2004/0193272, entitled“Instrumentation And Methods For Use In Implanting A Cervical DiscReplacement Device” and filed on Feb. 19, 2004, the disclosures of whichare hereby incorporated by reference herein.

The present application also relates to U.S. Pat. No. 6,607,559,entitled “Trial Intervertebral Distraction Spacers” and filed on Jul.16, 2001; U.S. patent application Ser. No. 10/436,039, entitled “TrialIntervertebral Spacers” and filed May 12, 2003; U.S. patent Ser. No.10/128,619, entitled “Intervertebral Spacer Having A Flexible Wire MeshVertebral Body Contact Element” and filed Apr. 23, 2002; U.S. patentapplication. Ser. No. 11/073,987, entitled Intervertebral Spacer HavingA Flexible Wire Mesh Vertebral Body Contact Element; U.S. patentapplication Ser. No. 10/140,153, entitled “Artificial IntervertebralDisc Having A Flexible Wire Mesh Vertebral Body Contact Element” andfiled May 7, 2002; U.S. patent application Ser. No. 10/151,280, entitled“Tension Bearing Artificial Disc Providing A Centroid Of MotionCentrally Located Within An Intervertebral Space” and filed May 20,2002; U.S. patent application Ser. No. 10/175,417, entitled “ArtificialIntervertebral Disc Utilizing A Ball Joint Coupling” and filed Jun. 19,2002; U.S. patent application Ser. No. 10/256,160, entitled “ArtificialIntervertebral Disc” and filed Sep. 26, 2002; U.S. patent applicationSer. No. 10/294,983, entitled “Artificial. Intervertebral Disc Having ACaptured Ball And Socket Joint With A Solid Ball And Retaining Cap” andfiled Nov. 14, 2002; U.S. patent application Ser. No. 10/294,982,entitled “Artificial Intervertebral Disc” and filed Nov. 14, 2002; U.S.patent application Ser. No. 10/294,981, entitled “ArtificialIntervertebral Disc Having A Captured Ball And Socket Joint With A SolidBall And Compression Locking Post” and filed Nov. 14, 2002; U.S. patentapplication Ser. No. 10/642,523, entitled “Axially CompresibleArtificial Intervertebral Disc Having Limited Rotation Using A CapturedBall and Socket” and filed Aug. 15, 2003; U.S. patent application Ser.No. 10/642,522, entitled Artificial Intervertebral Disc Having ACircumferentially Buried Wire Mesh Endplate Attachment Device and filedAug. 15, 2003; U.S. patent application Ser. No. 11/073,987, entitled“Intervertebral Spacer Device Having A Circumferentially Buried WireMesh Endplate Attachment Device” and filed Aug. 15, 2003; U.S. patentapplication Ser. No. 10/642,526, entitled “Circumferentially BuriedWired Mesh Endplate Attachment Device For Use With An Orthopedic Device”and filed Aug. 15, 2003; U.S. patent application Ser. No. 10/294,984,entitled “Artificial Intervertebral Disc Having Limited Rotation Using ACaptured Ball And Socket Joint With A Retaining Cap And A Solid BallHaving A Protrusion” and filed Nov. 14, 2002; U.S. patent applicationSer. No. 10/294,985, entitled “Artificial Intervertebral Disc HavingLimited Rotation Using A Captured Ball and Socket Joint With ACompression” and filed Ser. No. 10/294,985; U.S. patent application Ser.No. 10/294,980, entitled “Artificial Intervertebral Disc Having LimitedRotation Using A Captured Ball And Socket Joint With A Solid Ball, ARetaining Cap, And An Interference Pin” and filed Nov. 14, 2002; U.S.patent application Ser. No. 10/294,986, entitled “ArtificialIntervertebral Disc Having Limited Rotation. Using A Captured Ball andSocket Joint With A Solid Ball, A Compression Locking Post, And AnInterference Pin” and filed Nov. 14, 2002; U.S. patent application Ser.No. 10/282,356, entitled “Artificial Intervertebral Disc” and filed Sep.26, 2002; U.S. patent application Ser. No. 10/784,646, entitledArtificial Intervertebral Disc Trial Having A Controllably SeparableDistal End” and filed Feb. 23, 2004; U.S. patent application Ser. No.10/309,585, entitled “Static Trials And Related Instruments and MethodsFor Use In Implanting An Artificial Intervertebral Disc” and filed Dec.4, 2002; U.S. patent application Ser. No. 10/784,637, entitled“Instrumentation For Properly Seating An Artificial Disc In AnIntervertebral Space” and filed Feb. 23, 2004; U.S. patent applicationSer. No. 10/783,153, entitled “Parallel Distractor And Related MethodsFor Use In Implanting An Artificial Intervertebral Disc” and filed Feb.20, 2004, the disclosures of which are hereby incorporated by referenceherein.

BACKGROUND OF THE INVENTION

The present invention is directed to a spinal joint replacement implantand more particularly to a cervical intervertebral disc implant havingsaddle shaped articulating surfaces and to tooling and methods ofinserting the cervical intervertebral disc implant.

As is well known to those skilled in the art, the structure of theintervertebral disc disposed between the cervical bones in the humanspine comprises a peripheral fibrous shroud (the annulus) whichcircumscribes a spheroid of flexibly deformable material (the nucleus).The nucleus comprises a hydrophilic, elastomeric cartilaginous substancethat cushions and supports the separation between the bones while alsopermitting articulation of the two vertebral bones relative to oneanother to the extent such articulation is allowed by the other softtissue and bony structures surrounding the disc. The additional bonystructures that define pathways of motion in various modes include theposterior joints (the facets) and the lateral intervertebral joints (theunco-vertebral joints). Soft tissue components, such as ligaments andtendons, constrain the overall segmental motion as well.

Traumatic, genetic, and long term wearing phenomena contribute to thedegeneration of the nucleus in the human spine. This degeneration ofthis critical disc material, from the hydrated, elastomeric materialthat supports the separation and flexibility of the vertebral bones, toa flattened and inflexible state, has profound effects on the mobility(instability and limited ranges of appropriate motion) of the segment,and can cause significant pain to the individual suffering from thecondition. Although the specific causes of pain in patients sufferingfrom degenerative disc disease of the cervical spine have not beendefinitively established, it has been recognized that pain may be theresult of neurological implications (nerve fibers being compressed)and/or the subsequent degeneration of the surrounding tissues (thearthritic degeneration of the facet joints) as a result of their beingoverloaded.

Traditionally, the treatment of choice for physicians caring forpatients who suffer from significant degeneration of the cervicalintervertebral disc is to remove some, or all, of the damaged disc. Ininstances in which a sufficient portion of the intervertebral discmaterial is removed, or in which much of the necessary spacing betweenthe vertebrae has been lost (significant subsidence), restoration of theintervertebral separation is required.

Unfortunately, until the advent of spine arthroplasty devices, the onlymethods known to surgeons to maintain the necessary disc heightnecessitated the immobilization of the segment. Immobilization isgenerally achieved by attaching metal plates to the anterior orposterior elements of the cervical spine, and the insertion of someosteoconductive material (autograft, allograft, or other porousmaterial) between the adjacent vertebrae of the segment. Thisimmobilization and insertion of osteoconductive material has beenutilized in pursuit of a fusion of the bones, which is a procedurecarried out on tens of thousands of pain suffering patients per year.

This sacrifice of mobility at the immobilized, or fused, segment,however, is not without consequences. It was traditionally held that thepatient's surrounding joint segments would accommodate any additionalarticulation demanded of them during normal motion by virtue of thefused segment's immobility. While this is true over the short-term(provided only one, or at most two, segments have been fused), theeffects of this increased range of articulation demanded of theseadjacent segments has recently become a concern. Specifically, anincrease in the frequency of returning patients who suffer fromdegeneration at adjacent levels has been reported.

Whether this increase in adjacent level deterioration is trulyassociated with rigid fusion, or if it is simply a matter of theindividual patient's predisposition to degeneration is unknown. Eitherway, however, it is clear that a progressive fusion of a long sequenceof vertebrae is undesirable from the perspective of the patient'squality of life as well as from the perspective of pushing a patient toundergo multiple operative procedures.

While spine arthroplasty has been developing in theory over the pastseveral decades, and has even seen a number of early attempts in thelumbar spine show promising results, it is only recently thatarthroplasty of the spine has become a truly realizable promise. Thefield of spine arthroplasty has several classes of devices. The mostpopular among these are: (a) the nucleus replacements, which arecharacterized by a flexible container filled with an elastomericmaterial that can mimic the healthy nucleus; and (b) the total discreplacements, which are designed with rigid baseplates that house amechanical articulating structure that attempts to mimic and promote thehealthy segmental motion.

Among these solutions, the total disc replacements have begun to beregarded as the most probable long-term treatments for patients havingmoderate to severe lumbar disc degeneration. In the cervical spine, itis likely that these mechanical solutions will also become the treatmentof choice. At present, there are two devices being tested clinically inhumans for the indication of cervical disc degeneration. The first ofthese is the Bryan disc, disclosed in part in U.S. Pat. No. 6,001,130.The Bryan disc is comprised of a resilient nucleus body disposed inbetween concaval-covex upper and lower elements that retain the nucleusbetween adjacent vertebral bodies in the spine. The concaval-convexelements are L-shaped supports that have anterior wings that acceptbones screws for securing to the adjacent vertebral bodies.

The second of these devices being clinically tested is the Bristol disc,disclosed substantially in U.S. Pat. No. 6,113,637. The Bristol disc iscomprised of two L-shaped elements, with corresponding ones of the legsof each element being interposed between the vertebrae and in oppositionto one another. The other of the two legs are disposed outside of theintervertebral space and include screw holes through which the elementsmay be secured to the corresponding vertebra; the superior element beingsecured to the upper vertebral body and the inferior element beingattached to the lower vertebral body. The opposing portions of each ofthe elements comprise the articulating surfaces that include anelliptical channel formed in the lower element and a convexhemispherical structure disposed in the channel.

As is evident from the above descriptions, the centers of rotation forboth of these devices, which are being clinically tested in humansubjects, is disposed at some point in the disc space. More particularlywith respect to the Bryan disc, the center of rotation is maintained ata central portion of the nucleus, and hence in the center of the discspace. The Bristol disc, as a function of its elongated channel (itselongated axis being oriented along the anterior to posteriordirection), has a moving center of rotation which is at all timesmaintained within the disc space at the rotational center of thehemispherical ball (near the top of the upper element).

Thus, there remains a need for improved intervertebral discs, as well asnew and improved methods for safely and efficiently implantingintervertebral discs.

SUMMARY OF THE INVENTION

Disclosed herein are intervertebral discs or implants, surgicalinstruments and procedures in accordance with certain preferredembodiments of the present invention. It is contemplated, however, thatthe implants, instruments and procedures may be slightly modified,and/or used in whole or in part and with or without other instruments orprocedures, and still fall within the scope of the present invention.Although the present invention may discuss a series of steps in aprocedure, the steps can be accomplished in a different order, or beused individually, or in subgroupings of any order, or in conjunctionwith other methods, without deviating from the scope of the invention.

In certain preferred embodiments of the present invention, anintervertebral disc implant includes a top element 102 and a bottomelement 104. The top and bottom elements preferably have opposingarticulating surfaces that engage one another. The intervertebral discimplant is adapted to be inserted into a disc space between adjacentvertebrae. In certain preferred embodiments, two or more disc implantscan be stacked over one another in two or more successive disc spaces.In still other preferred embodiments, the disc implants are cervicalimplants.

The top element of the implant preferably includes a first bone engagingsurface having a protrusion and a second articulating surface. The topelement desirably includes a posterior end, an anterior end and anopening at the anterior end that is adapted to receive a prong or postof an insertion instrument. The top element desirably includes opposinglateral sides that extend between the posterior end and the anterior endof the top element. In certain preferred embodiments, the intervertebraldisc implant may be at least partially coated with an osteoconductivematerial to facilitate long-term fixation to endplates of vertebralbodies.

The articulating surface of the top element preferably defines a convexcurve or surface extending between the sides. The articulating surfacealso defines a concave curve or surface extending between the posteriorand anterior ends of the top element. In certain preferred embodiments,the articulating surface defines a toroidal saddle-shaped surface.

The protrusions on the top element preferably include teeth 122, whichdesirably have sloping surfaces. Each of the sloping surfaces preferablyhas a low point nearer to the posterior end of the top element and ahigh point nearer to the anterior end of the top element. The slopingsurfaces preferably facilitate insertion of the posterior end of the topelement into a disc space while making it more difficult for the topelement to be removed or discharged from the disc space in a posteriorto anterior direction.

The intervertebral disc implant preferably includes the bottom elementhaving a first bone engaging surface and a second articulating surfacethat is designed to engage the articulating surface of the top elementwhen the top and bottom elements contact one another. The bottom elementincludes a posterior end, an anterior end, and lateral sides extendingbetween the posterior end and the anterior end. The first bone engagingsurface of the second element includes first and second protrusions,with each protrusion preferably including teeth. The teeth desirablyinclude sloping surfaces having a low point nearer to the posterior endof the bottom element and a high point nearer to the anterior end of thebottom element. The sloping surfaces on the teeth of the bottom elementpreferably facilitate insertion of the bottom element into a disc space.The teeth have vertical surfaces, however, that hinder or preventdislodgement of the implant from the disc space. In certain preferredembodiments, the teeth on the top and bottom elements may have the samestructure, or one or more features of the teeth described above.

The bottom element desirably has two openings provided at the anteriorend thereof. The two openings are preferably adapted to receive theprongs or pins of an insertion instrument, as will be described in moredetail below. In certain preferred embodiments, the bottom element maybe at least partially coated with an osteoconductive material tofacilitate long-term fixation to a vertebral endplate.

The articulating surface of the bottom element preferably defines aconvex curve or surface extending between the posterior end and theanterior end of the bottom element. The articulating surface preferablydefines a concave curve or surface extending between the lateral sidesof the bottom element. As will be described in more detail herein, thearticulating surface preferably defines a toroidal saddle-shaped surfacethat engages the articulating surface of the top element when the topend bottom elements are in contact with one another.

When the top element is assembled with the bottom element, the opposingarticulating surfaces are adapted to engage one another. When the topand bottom elements are assembled together, the projection on the topelement is offset from the two projections on the bottom element. Inprior art devices, it has been observed that stacking two implants insuccessive disc spaces may result in cracking of vertebral bone betweenthe implants because the apexes on the teeth of the two implants are inalignment. The present invention seeks to avoid this cracking problem byoffsetting the projection on the top element from the projections on thebottom element. Although the present invention is not limited by anyparticular theory of operation, it is believed that providingprojections that are offset from one another enables two or moreintervertebral disc implants to be inserted into two or more successivedisc spaces, while minimizing the likelihood of cracking the vertebralbodies between the disc spaces.

Prior to insertion into an intervertebral space, the articulatingsurface of the top element opposes the articulating surface of thebottom element. In preferred embodiments, the articulating surface ofthe top element defines a toroidal saddle-shaped surface including aconcave surface extending between proximal and anterior ends thereof anda convex surface extending between the sides of the top element. Thearticulating surface of the bottom element also preferably includes atoroidal saddle-shaped surface having a convex surface extending betweenthe posterior and anterior ends and a concave surface extending betweenthe sides of the bottom element. The articulating surfaces may besimilar to the articulating surfaces disclosed in commonly assigned U.S.Pat. No. 6,997,955, the disclosure of which is hereby incorporated byreference herein.

In other preferred embodiments of the present invention, a kit forpreparing an intervertebral disc space for receiving an implant includesa plurality of trials having different sizes. Each trial preferablyincludes a body insertible into an intervertebral disc space, the bodyhaving a leading end, a trailing end, a top surface with a first grooveformed therein and a bottom surface with a second groove formed therein.The grooves preferably extend between the leading and trailing ends ofthe body. Each trial also desirably includes a flange secured to thetrailing end of the body, the flange having a first channel aligned withthe first groove and a second channel aligned with the second groove,wherein each of the different sized trials has a different flangethickness. Although the present invention is not limited by anyparticular theory of operation, it is believed that changing the flangethickness will limit the depth to which bone cutting instruments such asa chisel may be advanced into vertebral bone. Thus, in certain preferredembodiments, a smaller sized trial will have a thicker flange and alarger sized trial will have a thinner flange.

In certain preferred embodiments, the top surface of the body desirablytapers toward the bottom surface of the body between the trailing endand the leading end of the body. In other words, the leading end of thebody has a taper which facilitates insertion into a disc space.

The trial desirably includes a third groove formed in the bottom surfaceof the body, wherein the first groove is offset from the second andthird grooves, and the second and third grooves are spaced from oneanother. The flange preferably includes a third channel aligned with thethird groove in the body.

In preferred embodiments, the first channel has an upper end having afirst width and a lower end having a second width that is less than thefirst width. The first groove in the body preferably has a width that issubstantially the same as the first width of the first channel. Thesecond channel desirably has a lower end having a first width and anupper end having a second width that is less than the first width of thesecond channel. The second groove in the body desirably has a width thatis substantially the same as the first width of said second channel.

In another preferred embodiment of the present invention, an inserterhead for an intervertebral disc implant includes a body having a leadingend with a concave surface, whereby the concave surface has an upper endand a lower end. The inserted head preferably includes a first pinprojecting from the concave surface adjacent the upper end of theconcave surface, and a pair of second pins spaced from one another andprojecting from the concave surface adjacent the lower end of theconcave surface. The first pin may be resilient. The inserter headdesirably includes a wedge projecting from the concave surface and beingdisposed between the first pin and the pair of second pins.

The inserter head desirably includes a first flange projecting upwardlyfrom the body and a second flange projecting downwardly from the body.The first and second flanges are desirably adapted for engagingvertebral bone for limiting advancement of the inserter head into anintervertebral disc space. The inserter head may desirably include astem projecting from a trailing end of the inserter head for couplingthe inserter head to a handle.

In further preferred embodiments of the present invention, a combinationinserter head and intervertebral disc implant includes theintervertebral disc implant having a top element with a posterior end,an anterior end, an opening in the anterior end, a bone engaging surfaceand an articulating surface. The intervertebral disc implant preferablyhas a bottom element with a posterior end, an anterior end, a pair ofspaced openings in the anterior end, a bone engaging surface and anarticulating surface that opposes the articulating surface of the topelement.

In the combination, the inserter head preferably includes a body havinga leading end with a concave surface, the concave surface having anupper end and a lower end. The inserter head desirably has a first pin,such as a resilient pin, projecting from the concave surface adjacentthe upper end of the concave surface, a pair of second pins spaced fromone another and projecting from the concave surface adjacent the lowerend of the concave surface, and a wedge projecting from the concavesurface and being disposed between the first pin and the pair of secondpins. The first pin is disposed in the opening of the top element of theimplant and the pair of second pins are disposed in the pair of openingsin the bottom element of the implant.

As noted above, the first pin is preferably resilient for urging the topelement of the implant against the wedge of the inserter head. The pairof spaced second pins on the inserter head are desirably spaced from oneanother by a first distance and the pair of openings in the lowerelement of the implant are spaced from one another by a second distancethat is different than the first distance. In certain preferredembodiments, the first distance is greater than the second distance. Inother preferred embodiments, however, the first distance is less thanthe second distance. The different distances preferably form a frictionlock between the pair of pins and the pair of openings in the bottomelement.

In still other preferred embodiments of the present invention, a kit forstabilizing a spinal segment includes a plurality of two-partintervertebral disc implants having different sizes and a plurality ofinserter heads having different sizes, whereby each of the inserterheads is adapted for holding together one of the two-part intervertebraldisc implants as a single implantable unit.

The inserter head may have indicia corresponding to the size of theintervertebral disc implant held by the inserter head. The indicia mayinclude a color, code and/or text indicating the size of theintervertebral disc implant held by the inserter head.

Each intervertebral disc implant preferably has a top element includinga bone engaging surface, an articulating surface and an opening at ananterior end thereof, and a bottom element including a bone engagingsurface, an articulating surface and a pair of openings adjacent theanterior end thereof, whereby the inserter head includes pins insertibleinto the openings at the anterior end for holding the articulatingsurfaces of the top and bottom elements in contact with one another.

In certain preferred embodiments, the intervertebral disc implant, orthe instruments, may alternatively or additionally incorporate any orall of the features discussed previously, disclosed herein, or discussedin U.S. patents and/or patent applications incorporated by referenceherein. Preferably, the configuration of the bearing surfaces of theintervertebral disc implant in this preferred embodiment may besubstantially similar to those of the other bearing surfaceconfigurations discussed previously, disclosed herein, or incorporatedby reference herein.

It should be noted that features and methods and functionalities of thepresent invention, including but not limited to features and methods andfunctionalities for engaging one tool (or parts thereof) with one ormore other tools (or parts thereof) or with the implants (or partsthereof), and vice-versa; for addressing, avoiding, manipulating, orengaging the patient's anatomy; for aligning one or more tools withanatomic or non-anatomic reference points; and for aligning the toolsand implants with one another and/or a treatment space; are not andshould not be limited to those embodied in and achieved by thestructures and methods of the specific embodiments described and shown,but rather the structures and methods of the specific embodimentsdescribed and shown are merely examples of structures and methods thatcan achieve certain features and methods and functionalities of thepresent invention.

Another aspect of the present invention includes a method of performingspinal surgery including the steps of inserting a trial in anintervertebral disc space between two adjacent vertebrae, cutting aportion of at least one vertebrae while the trial is in theintervertebral disc space, removing the trial, and inserting a two-partintervertebral disc implant in the intervertebral disc space. The methodmay further include the step of attaching the two-part intervertebraldisc implant to an inserter head having a size corresponding to theimplant.

These and other preferred embodiments of the present invention will bedescribed in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a side elevational view of an intervertebral disc implanthaving a top element and a bottom element, in accordance with certainpreferred embodiments of the present invention.

FIG. 1B shows a perspective view of the intervertebral disc implantshown in FIG. 1A.

FIGS. 2A-2G show the top element of the intervertebral disc implantshown in FIGS. 1A and 1B.

FIGS. 3A-3G show the bottom element of the intervertebral disc implantshown in FIGS. 1A and 1B.

FIGS. 4A-4C show a combination trial and chisel guide used for preparingan intervertebral disc space for receiving the intervertebral discimplant shown in FIGS. 1A and 1B, in accordance with certain preferredembodiments of the present invention.

FIGS. 5A-5D show a chisel used with the combination trial and chiselguide of FIGS. 4A-4C, in accordance with certain preferred embodimentsof the present invention.

FIGS. 6A-6E show the chisel of FIGS. 5A-5D assembled with thecombination trial and chisel guide of FIGS. 4A-4C.

FIGS. 7A-7C show an inserter head for inserting the intervertebral discimplant of FIGS. 1A-1B into an intervertebral disc space, in accordancewith certain preferred embodiments of the present invention.

FIGS. 8A-8F show the inserter head of FIGS. 7A-7C coupled with theintervertebral disc implant of FIGS. 1A-1B.

FIGS. 9A-9D show a handle attachable to the combination trial and chiselguide of FIGS. 4A-4C and the inserter head of FIGS. 7A-7C, in accordancewith certain preferred embodiments of the present invention.

FIG. 10 shows a pusher rod, in accordance with certain preferredembodiments of the present invention.

FIGS. 11A-11C show the handle of FIGS. 9A-9C attached to the inserterhead of FIGS. 7A-7C.

FIGS. 12A-12C show the pusher rod of FIG. 10 coupled with the handle ofFIGS. 9A-9C.

FIG. 13 shows a combination trial and chisel guide, in accordance withone preferred embodiment of the present invention.

FIG. 14 shows a combination trial and chisel guide, in accordance withanother preferred embodiment of the present invention.

FIG. 15 shows a combination trial and chisel guide, in accordance withstill another preferred embodiment of the present

FIG. 16 shows a combination trial and chisel guide, in accordance withyet a further preferred embodiment of the present invention.

FIGS. 17A-17C show respective top plan, side elevational andcross-sectional views of an intervertebral disc implant coupled with aninserter head, in accordance with certain preferred embodiments of thepresent invention.

FIGS. 18A-18C show respective top plan, side elevational andcross-sectional views of an intervertebral disc implant coupled with aninserter head, in accordance with further preferred embodiments of thepresent invention.

DETAILED DESCRIPTION

Referring to FIGS. 1A and 1B, in certain preferred embodiments of thepresent invention, an intervertebral disc implant 100 includes a topelement 102 and a bottom element 104. As will be described in moredetail below, the top and bottom elements 102, 104 have opposingarticulating surfaces that engage one another. The intervertebral discimplant is adapted to be inserted into a disc space between adjacentvertebrae. In certain preferred embodiments, two or more disc implantscan be stacked over one another in two or more successive disc spaces.In still other preferred embodiments, the disc implants are cervicalimplants.

Referring to FIGS. 2A-2E, the top element 102 includes a first boneengaging surface 106 having a protrusion 108 and a second articulatingsurface 110. Referring to FIGS. 2E-2G, the top element 102 has aposterior end 112 and an anterior end 114. As shown in FIGS. 2A-2B and2D, the top element 102 has an opening 116 at the anterior end 114thereof that is adapted to receive a prong or post of an insertioninstrument, as will be described in more detail below. Referring toFIGS. 2C-2D and 2F-2G, the top element 102 has opposing lateral sides118, 120 that extend between the posterior end 112 and the anterior end114 of the top element. In certain preferred embodiments, theintervertebral disc implant may be at least partially coated with anosteoconductive material to facilitate long-term fixation to endplatesof vertebral bodies.

Referring to FIGS. 2C and 2D, the articulating surface 110 preferablydefines a convex curve or surface extending between the sides 118, 120of the top element 102. Referring to FIGS. 2A and 2E, the articulatingsurface 110 also defines a concave curve or surface extending betweenthe posterior and anterior ends 112, 114 of the top element 102. Incertain preferred embodiments, the articulating surface 110 defines atoroidal saddle-shaped surface.

As shown in FIGS. 2A-2E and 2G, the protrusion 108 preferably includesteeth 122. Referring to FIG. 2E, the teeth 122 desirably have slopingsurfaces 124, each sloping surface preferably having a low point nearerto the posterior end 112 of the top element 102 and a high point nearerto the anterior end 114 of the top element 102. Referring to FIGS. 2Eand 2G, the sloping surfaces 124 preferably facilitate insertion of theposterior end 112 of the top element 102 into a disc space while makingit more difficult for the top element to be removed or discharged fromthe disc space. Thus, referring to FIG. 2G, the sloping surfaces 124 ofthe teeth 122 facilitate insertion of the implant in a directionindicated by arrow D₁, while the vertical surfaces 126 (FIG. 2E) of theteeth 122 hinder or prevent dislodgement of the implant in the directionindicated by arrow D₂.

Referring to FIGS. 3A-3E, the intervertebral disc implant preferablyincludes the bottom element 104 having a first bone engaging surface 128and a second articulating surface 130 that is designed to engage thearticulating surface 110 of the top element 102 (FIG. 2A) when the topand bottom elements contact one another. The bottom element 104 includesa posterior end 132, an anterior end 134, and lateral sides 136, 138extending between the posterior end and the anterior end. Referring toFIGS. 3C-3D and 3G, the first bone engaging surface 128 of the secondelement includes first and second protrusions 140A, 140B, with eachprotrusion 140A, 140B preferably including teeth 144. Referring to FIGS.3E and 3G, the teeth include sloping surfaces 146 having a low pointnearer to the posterior end 132 of the bottom element 104 and a highpoint nearer to the anterior end 134 of the bottom element 104.Referring to FIG. 3G, similar to the sloping surfaces 146 of the teethof the top element 102 described above, the sloping surfaces 146 on theteeth 144 facilitate insertion of the bottom element 104 in thedirection indicated by arrow D₃. The teeth 144 have vertical surfaces147, however, that hinder or prevent dislodgement of the implant in thedirection indicated by arrow D₄.

Referring to FIGS. 3A-3B, 3D and 3F, the bottom element 108 has twoopenings 150A, 150B provided at the anterior end 134 thereof. Theopenings 150A, 150B are preferably adapted to receive the prongs of aninsertion instrument, as will be described in more detail below. Incertain preferred embodiments, the bottom element 104 may be at leastpartially coated with an osteoconductive material to facilitatelong-term fixation to a vertebral endplate.

Referring to FIGS. 3A and 3E, the articulating surface 130 preferablydefines a convex curve or surface extending between the posterior end132 and the anterior end 134 of the bottom element 104. Referring toFIGS. 3C and 3D, the articulating surface 130 preferably defines aconcave curve or surface extending between the lateral sides 136, 138 ofthe bottom element 104. As will be described in more detail herein, thearticulating surface 130 preferably defines a toroidal saddle-shapedsurface that engages the articulating surface 110 of the top element 102(FIG. 2A) when the top end bottom elements are in contact with oneanother.

FIGS. 1A and 1B show the top element 102 of FIG. 2A being assembled withthe bottom element 104 of FIG. 3A. The opposing articulating surfaces110, 130 of the respective top element 102 and the bottom element 104are adapted to engage one another. The teeth 122 on the top element 102slope downwardly toward the posterior end 112 of the top element.Similarly, the teeth 144 on the bottom element 104 slope downwardlytoward the posterior end 132 of the bottom element.

Referring to FIG. 1B, when the top and bottom elements 102, 104 areassembled together, the projection 108 on the top element 102 is offsetfrom the two projections 140A, 140B on the bottom element 104. In priorart devices, it has been observed that stacking two implants insuccessive disc spaces may result in cracking of vertebral bone betweenthe implants because the apexes on the teeth of the two implants are inalignment. The present invention seeks to avoid this cracking problem byoffsetting the projection 108 on the top element 102 from theprojections 140A, 140B on the bottom element 104. Although the presentinvention is not limited by any particular theory of operation, it isbelieved that providing projections 108, 140 that are offset from oneanother enables two or more intervertebral disc implants to be insertedinto two or more successive disc spaces, while minimizing the likelihoodof cracking the vertebral bodies between the disc spaces.

Referring to FIGS. 1A-1B, in preferred embodiments of the presentinvention, prior to insertion into an intervertebral space, thearticulating surface 110 of the top element 102 opposes the articulatingsurface 130 of the bottom element 104. In preferred embodiments, thearticulating surface 110 of the top element 102 defines a toroidalsaddle-shaped surface including a concave surface extending betweenproximal and anterior ends 112, 114 thereof and a convex surfaceextending between the sides 118, 120 of the top element 102. Thearticulating surface 130 of the bottom element 104 also preferablyincludes a toroidal saddle-shaped surface having a convex surfaceextending between the posterior and anterior ends 132, 134 and a concavesurface extending between the sides 136, 138 of the bottom element 104.

The articulating surfaces may be similar to the articulating surfacesdisclosed in commonly assigned U.S. Pat. No. 6,997,955, the disclosureof which is hereby incorporated by reference herein. In certainpreferred embodiments of the present invention, the longitudinallyinwardly directed articulation surface of the top element 102 forms aconstant radii saddle-shaped articulation surface. More particularly,the saddle surface is defined by a concave arc that is sweptperpendicular to and along a convex arc. The articulation surface has across-section in one plane that forms a concave arc, and a cross-sectionin another plane (perpendicular to that plane) that forms a convex arc.The concave arc has a respective constant radius of curvature about anaxis perpendicular to the one plane. The convex arc has a respectiveconstant radius of curvature about an axis perpendicular to the otherplane.

In a preferred embodiment, the concave arc has a constant radius ofcurvature A about an axis perpendicular to the anterior-posterior plane,and the convex arc has a constant radius of curvature B about an axisperpendicular to the lateral plane. Preferably, radius A is less thanradius B.

The longitudinally inwardly directed articulation surface of the bottomelement 104 also preferably forms a constant radii saddle-shapedarticulation surface. More particularly, the saddle-shaped surface isdefined by a convex arc that is swept perpendicular to and along aconcave arc. The articulation surface has a cross-section in one planethat forms a convex arc, and a cross-section in another plane(perpendicular to that plane) that forms a concave arc. The convex archas a respective constant radius of curvature about an axisperpendicular to the one plane. The concave arc has a respectiveconstant radius of curvature about an axis perpendicular to the otherplane.

In a preferred embodiment, the convex arc has a constant radius ofcurvature C about an axis perpendicular to the anterior-posterior plane,and the concave arc has a constant radius of curvature D about an axisperpendicular to the lateral plane. Preferably, radius C is less thanradius D.

The constant radii saddle shaped articulation surfaces of the top andbottom elements are configured and sized to be nestable against oneanother and articulatable against one another, to enable adjacentvertebral bones (against which the top and bottom elements arerespectively disposed in the intervertebral space) to articulate inflexion, extension, and lateral bending. More particularly, theintervertebral disc of the present invention is assembled by disposingthe top and bottom elements so that the vertebral body contact surfacesare directed away from one another, and the articulation surfaces arenested against one another such that the concave arcs accommodate theconvex arcs.

Accordingly, movement of the adjacent vertebral bones relative to oneanother is permitted by the movement of the top and bottom elementsrelative to one another. In flexion and extension, the concave arcs ofthe top element 102 ride on the convex arcs of the bottom element 104about a center of rotation below the articulation surfaces. In lateralbending, the concave arcs of the bottom element 104 ride on the convexarcs of the top element 102 about a center of rotation above thearticulation surfaces. During these articulations, the elements aremaintained at constant relative distraction positions, i.e., theelements do not move in directions that are directed away from oneanother (for example, do not move in opposing axial directions from oneanother (e.g., along a longitudinal axis of the spine)). Accordingly, incertain preferred embodiments, the present invention provides a pair ofarticulation surfaces that have a center of rotation above the surfacesin one mode of motion (e.g., lateral bending), and a center or rotationbelow the surfaces in another (e.g., flexion/extension), consistent inthese regards with the motion of a natural intervertebral joint, such asa cervical joint. Preferably, the articulation surfaces are sized andconfigured so that the respective ranges of angles through whichflexion/extension and lateral bending can be experienced are equal to orgreater than the respective normal physiologic ranges for such movementsin the cervical spine.

It is preferable that, in addition to the flexion, extension, andlateral bending motions described above, the adjacent vertebral bones bepermitted by the intervertebral disc implant to axially rotate relativeto one another (e.g., about the longitudinal axis of the spinal column)through a small range of angles without moving in opposite (or otherwisedirected away from one another) directions (e.g., along the longitudinalaxis) within that range, and then to engage in such opposite (orotherwise directed away from one another) movement once that range isexceeded. Preferably, the articulation surfaces are accordinglyconfigured and sized to permit such movements. Because of the differingradii of the opposing articulation surfaces, the top and bottom elementsare able to axially rotate relative to one another about thelongitudinal axis of the spinal column through a range of angles withoutcausing the vertebral body contact surfaces to move away from oneanother along the longitudinal axis. Once the axial rotation exceedsthat range, however, the articulation surfaces interfere with oneanother as the concave arcs move toward positions in which they would beparallel to one another, and the distance between the vertebral bodycontact surfaces increases with continued axial rotation as the concavearcs ride up against their oppositely directed slopes. Thus, thearticulation surfaces are configurable according to the presentinvention to permit normal physiologic axial rotational motion of theadjacent vertebral bones about the longitudinal axis through a range ofangles without abnormal immediate axially opposite (or otherwisedirected away from one another) movement, and to permit such axiallyopposite (or otherwise directed away from one another) movement whenunder normal physiologic conditions it should occur, that is, outsidethat range of angles.

The articulation surfaces preferably maintain contact over a range ofnormal physiologic articulating movement between the adjacent vertebralbones. That is, through flexion, extension, lateral bending, and axialrotation, the articulation surfaces are in contact with one another.Preferably, the surface area dimensions of the articulation surfaces areselected in view of the selected radii of curvature to prevent the edgesof the saddle surfaces (particularly the edges of the concave arcs) fromhitting any surrounding anatomic structures, or other portions of theopposing upper or lower element, before the limit of the normalphysiologic range of an attempted articulation is reached.

Referring to FIGS. 1A and 1B, the intervertebral disc implant 100includes the top element 102 and the bottom element 104. Thearticulating surface of the top element 102 preferably engages thearticulating surface of the bottom element 104. The articulating surfaceof the top element 102 defines a convex surface extending betweenlateral sides 118, 120 thereof and the articulating surface of thebottom element 104 defines a concave surface extending between thelateral sides 136, 138 thereof. After the opposing articulating surfacesare in contact with one another, the protrusion 108 on the top element102 is offset from the protrusion 140A, 140B on the bottom element 104.The offset protrusions preferably permit stacking of two intervertebraldisc implants in two successive disc spaces, while minimizing thelikelihood of cracking the vertebral bone between the adjacent discspaces. In other preferred embodiments, the offset protrusions enablethree or more intervertebral discs to be stacked atop one another overthree or more successive disc spaces.

Referring to FIG. 1B, the articulating surface 110 of the top element102 defines a concave surface extending between posterior 112 andanterior 114 ends thereof. The articulating surface 130 of the bottomelement 104 defines a convex surface extending between the posterior 132and anterior 134 ends thereof. The teeth 122 on the protrusion 108 ofthe top element 102 include sloping surfaces 124 that slope downwardlytoward the posterior end 112 of the top element 102. The teeth 144 onthe protrusions 140A, 140B of the bottom element 104 have slopingsurfaces 146 that slope downwardly toward the posterior end 132 of thebottom element 104. As a result, the sloping surfaces 124, 146 of therespective teeth 122, 144 slope in the same direction, i.e., toward theposterior ends of the top and bottom elements 102, 104. The respectivesloping surfaces 124, 146 facilitate insertion of the implant 100 into adisc space. The vertical surfaces 126, 147 on the respective teeth 122,144, however, hinder or prevent expulsion or migration of the implant100 from the disc space after it has been inserted.

FIGS. 4A-4C show a combination trial and chisel guide 152, in accordancewith certain preferred embodiments of the present invention. Referringto FIG. 4B, the trial 152 includes a body 154 having a top surface 156with a leading end 158 that is sloped and a bottom surface 160. Thetrial body 154 also includes a leading end 162 designed for insertioninto a disc space and a trailing end 164. The trial includes a flange166 connected with the trailing end 164 of the body 154. The flange 166includes an upper flange 168 that projects above top surface 156 of thebody 154 and a bottom flange section 170 that projects below the bottomsurface 160 of the body 154. The trailing end 164 of the body 154includes a stem 172 projecting therefrom. The stem 172 includes atapered section 174 that engages an end of a handle, as will bedescribed in more detail below.

Referring to FIG. 4A, the body 154 preferably includes a groove 176formed in the top surface 156 thereof. The groove 176 extends from theleading end 162 of the body toward the flange 166 at the trailing end ofthe body. The groove 176 guides advancement of a cutting blade on achisel for forming an opening in an end plate of a vertebral body toaccept the protrusion 108 of the top element 102, as will be describedin more detail below. In certain preferred embodiments of the presentinvention, it is contemplated that a chisel, broach or other cuttinginstrument may be used for forming the openings. A chisel typically hascutting edges along its axis. A chisel typically has just a singlecutting edge. As used herein, the term chisel is deemed to cover both achisel and a broach, or any other cutting tool that may be used to cutbone. The bottom surface of the body 154 preferably includes a pair ofgrooves (FIG. 6B) that are offset from the single groove 176 provided inthe top surface 156 of the body 154. The two grooves at the bottom ofthe body guide advancement of respective cutting blades on a chisel forforming openings in a second vertebral body that opposes the firstvertebral body to accept protrusions 140A and 140B of the bottom element104. Thus, the trial and chisel guide can be used for forming openingsin opposing vertebrae.

FIG. 4C shows a rear elevational view of the trial and chisel guideshown in FIGS. 4A and 4B. The upper flange portion 168 includes openings178A, 178B that are adapted to receive anchoring elements such as pinsor screws for temporarily securing the flange to bone. The upper flangeportion 168 also includes a channel 180 having a wider upper end 182 anda narrower lower end 184. The lower flange portion 170 includes a pairof channels 186A, 186B. The first channel 186A in the lower flangeportion 170 has a wider section 188A that becomes narrower at an upperend 190A thereof. The lower flange section 170 also includes the secondchannel 186B having a lower end 188B that is wider in an upper end 190Bthat is narrower. The cutting blades on the chisel pass through thewider upper ends 182, 188A and 188B of the channels. The cutting bladesof the chisel are too wide to pass through the narrow sections 184, 190Aand 190B of the channels. The narrow sections 184, 190A and 190B of thechannels provide a relief for cut bone chips and particles to escape.

As shown in FIG. 4C, the channel 180 in the upper flange part 168 isoffset from the two channels 186A, 186B in the lower flange portion 170.The respective channels 180, 186A, 186B are aligned with the respectivegrooves formed in the upper and lower surfaces of the body of the trial154.

Referring to FIGS. 4A and 4B, in certain preferred embodiments of thepresent invention, a plurality of trial and chisel guides havingdifferent sizes are provided in a kit. The different sized trials areused to determine the correct size for an intervertebral disc implant tobe placed in a disc space. Each of the trial and chisel guides may havea body having a different size. The differently sized bodies of thetrials may have a different width, height and/or, depth. In addition,the thickness of the flange 166 for the trial may vary. Although thepresent invention is not limited by any particular theory of operation,it is believed that the thickness of the flange will control how far thecutting blades on a chisel may advance into the grooves on a trial bodyfor controlling the depth of cutting into the vertebral bodies.

FIGS. 5A-5C show a chisel 192 used for forming openings in opposingvertebral bodies that accept the protrusions of the top element 102 andthe bottom element 104, in accordance with certain preferred embodimentsof the present invention. Referring to FIGS. 5B and 5C, the chisel 192includes a leading end 194 and a trailing end 196. The chisel includes ahandle 198 extending between the leading and trailing ends and astriking surface 200 provided at the trailing end. As will be describedin more detail below, after the chisel is assembled with the trial, ahammer, mallet or other similar instrument may be struck against thestriking surface 200 for advancing the chisel through the grooves in thebody of the trial and into vertebral bone.

Referring to FIG. 5A, the leading end 194 of the chisel 92 includes afirst cutting blade 202 adapted to form an opening in a first vertebralbody and second cutting blades 204A, 204B for forming openings in asecond vertebral body. Referring to FIG. 5B, the chisel includes a notch206 provided near the leading end thereof that is adapted to accommodatethe base 173 of the stem 172 (FIG. 4A) of the trial. When the chisel 192is assembled with the trial 154 (FIG. 4A), the first cutting bladeslides in the groove provided in the upper surface of the trial and thesecond cutting blades 204 slide in the grooves provided in the bottomsurface of the trial. Referring to FIGS. 5C and 5D, the first cuttingblade 202 of the chisel is offset from the pair of second cutting blades204A, 204B.

FIGS. 6A-6E show the chisel 192 of FIG. 5A being assembled with thetrial 154 of FIG. 4A. As shown in FIG. 6A, the first cutting blade 202slides through channel 180 and groove 176 for cutting a first keelopening in an end face of a first vertebral body. Referring to FIGS. 6Aand 6B, the pair of second cutting blades 204A, 204B pass throughchannels 186A, 186B of lower flange portion 170 and through grooves (notshown) provided in the bottom surface 160 of the trial.

FIG. 6D shows the pair of second cutting blades 204A, 204B extended overthe bottom surface of the trial and first cutting blade 202 extendingover the top surface of the trial.

In one preferred embodiment of the present invention, a surgeon selectsone of the combination trial and chisel guides from a kit. After thetrial and chisel guide is attached to a distal end of a handle (FIGS. 9Aand 9B), the surgeon inserts the body of the trial into the disc spaceand observes and senses whether the selected trial is the correct size.If the trial is not the correct size, then the surgeon will select atrial having a different size and insert that trial into the disc space.The surgeon will continue to evaluate trials having different sizesuntil a correctly sized trial has been identified. At that point, thesurgeon will note the size of the trial and will use the sizeinformation for selecting an appropriately sized chisel andintervertebral disc implant.

The surgeon will then use the correctly sized trial to form the openingsin the opposing faces of the vertebral bodies. While maintaining thebody of the trial in the disc space, the surgeon will secure the flange166 to bone by passing pins or screws through the openings 178A, 178B inthe flange (FIG. 4C). The chisel 192 shown in FIGS. 5A-5D will then beassembled with the trial so that the cutting blades are advanceable inthe grooves in the body of the trial. A mallet or hammer may be used fordriving the cutting blades into the vertebral bodies for forming theabove-discussed openings for accepting the protrusions of the top andbottom portions, 102 and 104, respectively.

In certain preferred embodiments, a plurality of combination trial andchisel guides of different sizes are provided. The bodies of the trialand chisel guides may have different sizes, heights, lengths and/orwidths. The flanges provided at the trailing ends of the bodies may alsohave different thicknesses. In further preferred embodiments, aplurality of chisels are provided, each chisel being size specific tothe trial selected. Thus, the prongs of a first chisel may be longerthan the prongs of a second chisel so that the respective chisels cutchannels in bone having different lengths.

FIGS. 7A-7C show an inserter head 210 used for inserting anintervertebral disc implant into a disc space, in accordance withcertain preferred embodiments of the present invention. Referring toFIG. 7A, the inserter head 210 preferably includes a body 212 having aconcave surface 214 at a leading end thereof. Referring to FIGS. 7A and7B, the body 212 preferably includes a top flange 216 projecting from anupper end thereof and a bottom flange 218 projecting from a lower endthereof. The flanges 216, 218 limit advancement of the inserter head 210into an intervertebral disc space. The body 212 includes a wedge 220having a sloping surface. In addition, the leading end of the body 212includes a first pin 222 adapted to engage the opening in the topelement of the intervertebral disc implant (FIG. 1A). The first pin 222is preferably resilient. When the first pin 222 is inserted into theopening 116 in the top element 102 of the implant (FIG. 2B), theresilient pin 222 presses the articulating surface 110 of the topelement against the sloping surface 220 of the wedge 220.

The leading end of the body of the inserted head also preferablyincludes a pair of second pins 224A, 224B that are adapted to engage thepair of openings 150A, 150B in the bottom element 104 of theintervertebral disc implant (FIG. 3D). The distance between the secondpins 224A, 224B preferably defines a distance that is different than thedistance between the openings 150A, 150B in the bottom element on theimplant. In one preferred embodiment, the distance between the pins isslightly wider than the distance between the openings 150A, 150B. Inanother preferred embodiment, the distance between the pins is slightlynarrower than the distance between the openings 150A, 150B. Thesedifferences preferably form a friction lock between the second pins224A, 224B and the openings 150A, 150B (FIG. 3D) in the bottom element.The inserter head preferably has a tapered stem 225 at a trailing endthereof that is adapted to be received in a tapered opening at a leadingend of a handle, as will be described in more detail below.

Referring to FIGS. 8A-8C, the inserter head 210 is adapted to secure thetop and bottom elements of the intervertebral disc implant 100.Referring to FIGS. 8D and 8E, the bottom pins 224 of the inserter head210 slide into the openings 150 in the bottom element 104 of theimplant. Referring to FIGS. 8D and 8F, the first resilient pin 222 onthe inserted head 210 slides into the opening 116 in the top element 102of the implant. The first resilient pin urges the articulating surfaceof the top element against the wedge for securing the top element to theinserted head.

FIGS. 9A-9D show a handle 230 having a leading end 232, a trailing end234 and a shaft 236 that extends between the leading and trailing ends.The leading end 232 of the shaft 236 includes a slot 238 formed thereinthat enables the leading end of the shaft to flex outwardly. Referringto FIG. 9B, the leading end 232 of the shaft 236 also includes a notch240 that is adapted to slide over the flanges 216, 218 of the inserterhead 210 (FIG. 7B) when the handle is assemble with the inserter head.Referring to FIG. 9D, the handle 230 has an opening 239 at the leadingend that is tapered. The tapered opening 239 of the handle preferablyaccommodates the tapered stem 225 of the inserter head 210 (FIG. 7B).The tapered opening 239 of the handle 230 may also accommodate taperedstems on the plurality of combination trial and chisel guides (FIG. 4A).Referring to FIGS. 9A-9C, the trailing end 234 of the handle 230includes a striking surface 240 that may be struck with a hammer ormallet for advancing the leading end 232 of the handle 230 toward anintervertebral disc space. The shaft 236 preferably has an opening thatextends along the length thereof from the leading end 232 to thetrailing end 234.

In certain preferred embodiments of the present invention, a pusher rod244 includes a shaft 246 having a leading end 248 and a trailing end250. The trailing end 250 of the shaft 246 includes a radially extendingflange 252 having a striking surface 254. The shaft 246 preferablyslides within the opening of the handle 230 (FIG. 9A).

FIGS. 11A-11C show the leading end of the handle 230 of FIGS. 9A-9Csecured to the inserter head 210 of FIG. 8A. In turn, the inserter head210 is holding the top and bottom elements 102, 104 of theintervertebral disc implant. The notches 240 at the leading end of theshaft 236 accommodate the flanges 216, 218 on the inserter head 210.

In certain preferred embodiments of the present invention, the handle230 is used to insert the implant 100 into a prepared disc space. Thecorrect size of the implant to be inserted into the disc space waspreferably previously determined using the combination trial and chiselguide shown and described above in FIGS. 4A-4C. Referring to FIGS.12A-12C, in order to disengage the implant 100 from the inserter head210, the shaft 246 of the pusher rod 244 is advanced into the elongatedopening extending through the handle 230 and advanced until the leadingend of the pusher rod engages the intervertebral disc implant 100. Thepusher rod 244 is further advanced for disengaging the implant 100 fromthe inserter head 210.

Referring to FIGS. 13 and 14, in accordance with certain preferredembodiments of the present invention, a surgical kit includes aplurality of trial and chisel guides 152. The trial and chisel guides152A, 152B have respective bodies 154A, 154B having the same sizes (i.e.same length, width and height). In the particular embodiment shown inFIGS. 13-14, however, the first trial and chisel guide 152A (FIG. 13)has a flange 166A having a first thickness T₁ and the second trial andchisel guide 152B (FIG. 14) has a flange 166B having a second thicknessT₂. The flange thickness T₂ of the second trial and chisel guide 152B ispreferably greater than the thickness T₁ of the first trial and chiselguide 152A. As shown in FIGS. 13 and 14, the flange thickness controlshow far the cutting blades 202, 204A, 204B of the chisel 192 may advancetoward the leading ends 162A, 162B of the respective trial and chiselguides 152A, 152B. When the same sized chisel 192 having cutting bladesof the same length is used, the different flange thicknesses willcontrol the depth of the channels cut into the vertebral bone. Inpreferred embodiments, the kit may include a plurality of trial andchisel guides having flanges having different thicknesses. In stillother preferred embodiments, a surgical kit may have a plurality oftrial and chisel guides having a plurality of different sized bodiesand/or a plurality of flanges having different thicknesses and/or aplurality of chisels having cutting blades of different lengths.

Referring to FIGS. 15 and 16, in accordance with certain preferredembodiments of the present invention, a surgical kit includes aplurality of trial and chisel guides 252A and 252B. At least some of thetrial and chisel guides 252 in the kit preferably have different sizes.Although only two trial and chisel guides are shown, the kit may includemany more trial and chisel guides. In the particular embodiment shown inFIGS. 15-16, a first trial and chisel guide 252A (FIG. 15) has a smallerbody 254A and a second trial and chisel guide 252B (FIG. 16) has alarger body 254B. The respective bodies may differ in size by lengthand/or width and/or thickness. Even though the trial and chisel guideshave bodies with different sizes, both guides have flanges 266A, 266Bhaving the same thickness T₃. In order to control the depth of the cutinto the vertebral bone, chisels having cutting blades having differentlengths, widths and/or heights may be provided. In FIG. 15, a firstchisel 292A having cutting blades having a length L₁ is coupled withtrial and chisel guide 252A. In FIG. 16, a second chisel 292B havingcutting blades having a length L₂ is used. Even though the flangethickness T₃ of the respective trial and chisel guides 252A, 252B arethe same, the second chisel 292B is able to cut further into bone due tothe longer cutting blades 302B, 304A and 304B on the second chisel. Inother preferred embodiments, a plurality of chisels having differentcutting blade lengths may be used. In still other preferred embodiments,as noted above, a plurality of chisels having cutting blades havingdifferent lengths, widths and/or heights may be provided.

As noted above, in certain preferred embodiments, a plurality of discimplants having different sizes may be provided. The particular sizeselected for insertion into the disc space is related to the size of theintervertebral space. Each disc implant may be coupled with an inserterhead having a size that matches the size of the disc implant. Thus, aplurality of inserter heads having different sizes may be provided,whereby each inserter head is sized to be coupled with an intervertebraldisc implant having a particular size.

In FIGS. 17A-17C, a first disc implant 110A is coupled with a firstinserter head 210A. In FIGS. 18A-18C, a second disc implant 110B, whichis larger than the first disc implant 100A, is coupled with a secondinserter head 210B that is larger than the first inserter head 210A.Other sized disc implants and inserter heads may also be provided.

In still other preferred embodiments of the present invention, asurgical kit may include chisels having different sizes such as cuttingblades having different lengths, widths and/or heights that may be usedfor forming channels in bone having different lengths, widths and/orheights. The particular chisel selected may relate to the size of theimplant being used. In certain preferred embodiments, the differentlysized implants have differently sized bone engaging elements (e.g. teethor bone engaging projections), thereby requiring differently sized trialand chisel guides and/or chisels for preparing the disc spaces.

In certain preferred embodiments, a plurality of inserter heads, eachholding a different sized implant, are provided. After the surgeon hasdetermined the correct size needed for the implant, the surgeon willselect the appropriate inserter head that holds the correctly sizedimplant. The surgeon will then attach the inserter head to the leadingend of the handle for inserting the implant into the prepared discspace. The handle and the attached inserter head are then removed,leaving the implant in the disc space. The inserter head may then beremoved from the handle using the pusher rod.

Prior to implanting the intervertebral disc implant, a review of X-rays,MRI or CT-myelogram is preferably conducted to assess the level to betreated for osteophytes and to compare the intervertebral disc heightwith the adjacent levels. The patient may be positioned in the supineposition to provide for an anterior surgical approach to the cervicalspine. Steps should preferably be taken to stabilize the patient's spinein a neutral position and to prevent rotation during the procedure. Incertain preferred embodiments, it may be preferable to place a towel orbean bag underneath the patient's shoulders. Tape, a halter or skeletaltraction may be used to prevent rotation.

In certain preferred embodiments, a transverse skin incision may be madeat the appropriate level to expose the targeted spinal segment includingthe discs above and below the target spinal segment. Care should betaken to avoid prolonged retraction pressure on vital structures, suchas the esophagus.

Another step in the intervertebral disc implantation procedure mayinvolve identifying and marking a midline on the target segment of thespine. In certain preferred embodiments, a template is utilized to markthe midline. The size and dimensions of the template may vary. The exacttemplate size selected may be based upon initial estimation of theappropriate implant size from pre-operative X-rays and/or MRI/CT. Instill other preferred embodiments, fluoroscopy may be used to verify themidline and lateral margins of the disc space. In addition, the spinousprocesses are preferably centered.

A tool such as a scalpel or an electrocautery tool is preferablyutilized to score the midline points on the anterior surfaces of thesuperior and inferior vertebral bodies. Care is preferably taken toensure that the midline is well defined for all subsequent endplatepreparation and implant insertion steps. A cutting tool such, as ascalpel may be used to dissect a window in the annulus of the targeteddisc. The size of the window dissected in the annulus preferablyapproximates the width of an intervertebral disc implant to be insertedtherein. In certain preferred embodiments, radiographic imaging such asfluoroscopy may be used to identify osteophytes that extend anteriorly.Any osteophytes that extend anteriorly are preferably resected back tothe vertebral body so that the surfaces of the superior and inferiorvertebral bodies are flattened. Moreover, techniques such asradiographic imaging may be used to identify any osteophytes extendingdownwardly or upwardly into the anterior region of the disc space. Suchosteophytes should be resected to the endplates.

After the targeted spinal segment has been distracted, the discectomyprocedure is completed. In preferred embodiments, the posterior andlateral margins of the disc space are cleared of any extraneous matter.The clearing of the lateral and posterior margins preferably extends tothe uncinate processes and all the way back to the nerve root and canal.In certain preferred embodiments, lateral fluoroscopy is utilized tocheck the anterior aspects of the vertebral body for osteophytes. Acutting tool, such as a burr, may be used to further prepare theendplates of the opposing superior and inferior vertebral bodies. Thecutting tool may be utilized to smooth out the curvatures of theendplates. After the discectomy has been completed, the endplates of theadjacent vertebral bodies are preferably parallel to one another andrelatively uniform, thereby preventing undersizing of the implant.

In certain preferred embodiments, the decompression of the targeted discspace may be completed by removing any posterior osteophytes or softtissue material that may inhibit the full distraction of the posteriorportion of the targeted disc space. In certain preferred embodiments, itmay be necessary to remove the posterior longitudinal ligament (PLL) toachieve optimal restoration of the disc height, decompression andrelease for post-operative motion. In addition, the posteriolateralcorners of the endplates may be resected as needed to provide neuraldecompression. In certain instances, it may be necessary to remove theposteriolateral uncovertebral joints. The lateral uncovertebral jointsare preferably not removed unless they are causing nerve rootcompression. In addition, in certain preferred embodiments it may benecessary to perform a foraminotomy if there are symptoms ofneural/foraminal stenosis.

In certain preferred embodiments, an appropriately sized intervertebraldisc implant is selected and inserted into a targeted disc space. Incertain preferred embodiments, the intervertebral disc implant isprovided as a single unit with the top and bottom elements of theimplant being held together by an implant dispenser (not shown). Inpreferred embodiments, the dispenser is color coded to correspond to theheight of the implant. In addition, the dispenser is preferably markedwith the height of the implant and the width of the top and bottomelements. The outer surface of the implant may also be marked with theheight and width of the implant, as well as the inferior/superiororientation. In particular preferred embodiments, the anterior face ofthe implant is marked with the height and width of the implant.

In preferred embodiments, prior to insertion of the intervertebral discimplant, the size label on the implant is inspected and the size labelon the dispenser is also inspected to ensure that the correctly sizedimplant was selected and that the top element of the implant is orientedfor proper insertion. In preferred embodiments, an implant is selectedhaving a height and baseplate dimensions that match the correspondingtrial that restored the desired height of the disc space withoutover-tensioning the annulus or damaging the facets.

After an appropriately sized intervertebral disc implant has beenselected, an inserter head, such as the inserter head shown anddescribed above in FIGS. 7A-7C, is selected. The selected inserter headpreferably has a height and/or dimensions that match the particulardimensions of the selected implant and selected implant dispenser. Thus,a plurality of insert heads having different sizes may be provided andthe inserter heads may also be color coded to correspond to the heightof the implant and the particular dimensions of the implant dispenser.The inserter head may be a single use component that is discarded afterthe implantation procedure.

In certain preferred embodiments, the implant is attached to theinserter head by first matching the superior and inferior labels on theimplant dispenser with the inserter head. The pins on the inserter headare then slid into the openings at the anterior ends of the top andbottom elements. The implant is preferably secured to the inserter headwhen the pins are seated in the openings of the top and bottom elements.Once the implant has been secured to the inserter head, the implantdispenser may be decoupled from the implant. Once secured thereto, theposterior ends of the top and bottom elements of the implant preferablyextend beyond the ends of the pins of the inserter head. The implantdispenser may then be detached from engagement with the implant.

In certain preferred embodiments, the intervertebral disc implant isinserted into a prepared disc space. The inserter head is properlyoriented with the disc space. In preferred embodiments, the inserterhead includes at least one label or marking that is oriented relative tothe superior or inferior vertebral bodies. Preferably, a superior labelof the inserter head is oriented on top and an inferior label isoriented on the bottom. As the intervertebral disc is advanced towardthe disc space, the implant protrusions/teeth are preferably alignedwith the openings previously formed in the endplates. In certainpreferred embodiments, fluoroscopy is utilized to check the angle ofinsertion of the implant. In certain preferred embodiments, the inserterhead is preferably advanced toward the disc space until the upper andlower flanges of the inserter head come into contact with the anteriorsurfaces of the adjacent vertebral bodies.

In certain preferred embodiments, insertion is completed when theimplant is fully disengaged from the inserter head and the top andbottom elements of the implant are positioned between the superior andinferior vertebral bodies. The anterior/posterior positioning of theimplant is preferably confirmed to be satisfactory using fluoroscopy. Ifmore posterior positioning of either the top element or the bottomelement of the intervertebral disc implant is required, a tamp may beutilized for adjusting the position of the implant. In preferredembodiments, the tamp may be impacted to adjust the anterior/posteriordepth of the top and bottom elements of the implant.

An intraoperative lateral and anterior/posterior image of the implantmay be obtained to observe its final position. If the implant is notproperly positioned, it may be removed such as by using an extractor.Once it has been confirmed that the intervertebral disc is properlypositioned within the disc space, a standard surgical closure procedurefor anterior spinal surgery may be performed. Prior to discharge fromthe hospital, a lateral and anterior/posterior X-ray with the patient inthe standing and/or sitting position is preferred.

Following surgery, in certain preferred embodiments, a goal ofpost-operative rehabilitation is to return the patient to normalactivity as soon as possible without jeopardizing soft and hard tissuehealing. Preferably, the patient should wear a soft collar forapproximately 1-2 weeks to support healing of the incision. Thepatient's rehabilitation program may be modified under the direction ofa surgeon to take into consideration the patient's age, stage ofhealing, general health, physical condition, life-style, and activitygoals. Adherence to a recommended rehabilitation program is highlydesirable.

Disclosed herein are implants, surgical instruments and procedures inaccordance with certain preferred embodiments of the present invention.It is contemplated, however, that the implants, instruments andprocedures may be slightly modified, and/or used in whole or in part andwith or without other instruments and procedures, and still fall withinthe scope of the present invention. Although the present, invention maydiscuss a series of steps in a procedure, the steps may be accomplishedin a different order, or may be used individually, or in conjunctionwith other methods, without deviating from the scope of the presentinvention.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

INDUSTRIAL APPLICABILITY

The present invention enjoys wide industrial applicability including,but not limited to, providing implants and instruments useful in spinalsurgery.

1. A kit for preparing an intervertebral disc space for receiving animplant comprising: a plurality of trials having different sizes, eachsaid trial comprising: a body insertible into an intervertebral discspace, said body having a leading end, a trailing end, a top surface anda bottom surface, said top surface of said body having a first grooveformed therein; and a flange secured to said trailing end of said body,said flange having a first channel aligned with said first groove,wherein each of said different sized trials has a different flangethickness.
 2. The kit as claimed in claim 1, wherein said first grooveextends between said leading and trailing ends of said body.
 3. The kitas claimed in claim 1, wherein said top surface of said body taperstoward said bottom surface of said body between said trailing end andsaid leading end of said body.
 4. The kit as claimed in claim 1, furthercomprising second and third grooves formed in said bottom surface ofeach said body, wherein said first groove is offset from said second andthird grooves.
 5. The kit as claimed in claim 4, wherein said second andthird grooves are spaced from one another.
 6. The kit as claimed inclaim 4, wherein said flange includes a second channel aligned with saidsecond groove in said body and a third channel aligned with said thirdgroove in said body.
 7. The kit as claimed in claim 1, wherein saidfirst channel has an upper end having a first width and a lower endhaving a second width that is less than the first width.
 8. The kit asclaimed in claim 7, wherein said first channel has a width that issubstantially the same as the first width of said first channel.
 9. Thekit as claimed in claim 6, wherein said second channel has a lower endhaving a first width and an upper end having a second width that is lessthan the first width of said second channel, and wherein said thirdchannel has a lower end having a first width and an upper end having asecond width that is less than the first width of said third channel.10. The kit as claimed in claim 9, wherein said second groove has awidth that is substantially the same as the first width of said secondchannel and said second groove has a width that is substantially thesame as the first width of said third channel.
 11. An inserter head foran intervertebral disc implant comprising: a body having a leading endwith a concave surface; said concave surface having an upper end and alower end; a first pin projecting from said concave surface adjacentsaid upper end of said concave surface; a pair of second pins spacedfrom one another and projecting from said concave surface adjacent saidlower end of said concave surface; a wedge projecting from said concavesurface and being disposed between said first pin and said pair ofsecond pins.
 12. The inserter head as claimed in claim 11, wherein saidfirst pin is resilient.
 13. The inserter head as claimed in claim 11,further comprising: a first flange projecting upwardly from said body;and a second flange projecting downwardly from said body, wherein saidfirst and second flanges are adapted for engaging vertebral bone forlimiting advancement of said inserter head into an intervertebral discspace.
 14. The inserter head as claimed in claim 11, further comprisinga stem projecting from a trailing end of said inserter head for couplingsaid inserter head to a handle.
 15. A combination inserter head andintervertebral disc implant comprising: an intervertebral disc implanthaving a top element with a posterior end, an anterior end, an openingin the anterior end, a bone engaging surface and an articulatingsurface; said intervertebral disc implant having a bottom element with aposterior end, an anterior end, a pair of spaced openings in theanterior end, a bone engaging surface and an articulating surface thatopposes the articulating surface of the top element; said inserter headincluding a body having a leading end with a concave surface, saidconcave surface having an upper end and a lower end; said inserter headhaving a first pin projecting from said concave surface adjacent saidupper end of said concave surface, a pair of second pins spaced from oneanother and projecting from said concave surface adjacent said lower endof said concave surface, and a wedge projecting from said concavesurface and being disposed between said first pin and said pair ofsecond pins, wherein said first pin is disposed in said opening of saidtop element of said implant and said pair of second pins are disposed insaid pair of openings in said bottom element of said implant.
 16. Thecombination as claimed in claim 15, wherein said first pin is resilientand urges said top element of said implant against said wedge of saidinserter head.
 17. The combination as claimed in claim 15, wherein saidpair of spaced second pins on said inserter head are spaced from oneanother by a first distance, and said, pair of openings in said lowerelement of said implant are spaced from one another by a second distancethat is different than the first distance for forming a friction lockbetween said pair of second pins and said bottom element.
 18. Thecombination as claimed in claim 17, wherein the first distance isgreater than the second distance.
 19. The combination as claimed inclaim 17, wherein the first distance is less than the second distance.20. A kit comprising: a plurality of two-part intervertebral discimplants having different sizes; and a plurality of inserter headshaving different sizes, each said inserter head being adapted forholding together one of said two-part intervertebral disc implants as asingle implantable unit, wherein each said inserter head has indiciacorresponding to the size of said intervertebral disc implant held bysaid inserter head.
 21. The kit as claimed in claim 20, wherein saidindicia includes a color code.
 22. The kit as claimed in claim 20,wherein said indicia includes text indicating the size of saidintervertebral disc implant held by said inserter head.
 23. The kit asclaimed in claim 20, wherein each said intervertebral disc implant has atop element including a bone engaging surface, an articulating surfaceand an opening at an anterior end thereof, and a bottom elementincluding a bone engaging surface, an articulating surface and a pair ofopenings at an anterior end thereof, wherein said inserter head includespins insertible into the openings at said anterior ends for holding saidarticulating surfaces of said top and bottom elements in contact withone another.
 24. A method of performing spinal surgery comprising thesteps: inserting a trial in an intervertebral disc space between twoadjacent vertebrae; cutting a portion of at least one vertebrae whilethe trial is in the intervertebral disc space; removing the trial; andinserting a two-part intervertebral disc implant in the intervertebraldisc space.
 25. The method of claim 24, further comprising the step ofattaching the two-part intervertebral disc implant to an inserter headhaving a size corresponding to the implant.